Back before Prohibition, before the rise of the "master distiller" as we know them today, the people who made whiskey in America were often referred to as 'distiller and yeast maker.' Booker Noe used to tell the story about how his grandfather, Jim Beam, made yeast on the back porch of his house in Bardstown. That yeast is still used to make Jim Beam bourbon.
If your intention is to be a craft distiller, making your own yeast would seem like something you would want to do, yet very few have messed around with it and no one is using their own yeast in production.
You don't 'make' yeast, of course, since yeast is a type of fungus, a living organism. You capture and propagate it. In the old days, before there were commercial yeast manufacturers, every distiller had his own secret yeast mash recipe and yeast-making technique, which was handed down from father to son.
Sour mash, which most microdistillers also do not use, was developed as a way to control yeast and make it perform consistently from batch to batch.
Most of the old timers who are still around will tell you that handling yeast is one of a distiller's most important skills, the first thing you are taught, because if you can't master that you shouldn't bother with the rest. They're mostly talking about propagating an existing jug yeast strain, to scale it up for production, not making it from scratch. Few distillers (micro or macro) even do that. For most of them, yeast comes in a bag.
I ask bourbon distillers about yeast-making from time to time. I once asked a member of the Beam family if he thought there was anyone still alive who could do it. He thought for a long time and answered, "maybe."
Here is what I know about the way old timers did it in Kentucky and Tennessee. You started with a proprietary yeast mash recipe. A mash for starting yeast is very different from a bourbon mash. It is mostly malt with little if any corn (ironically), plus ingredients such as sulfur and hops. The typical container was a bucket.
Booker remembered his grandmother complaining about how it stunk up the house.
They would mix up a batch, pick a place and wait. When it started to work they judged it by sight, smell, and taste. Maybe even sound. They didn't use microscopes. If they didn't like it, they dumped it out and tried again. They didn't modify the mash -- they knew that worked because it was the recipe their daddy used -- but they might change location. They knew it was largely a trial-and-error process, as much luck and patience as anything.
If they liked the initial action of the yeast, they started to propagate it. If it propagated well, which means it seemed robust and retained its characteristics (which meant it wasn't mutating too much), they would try pitching it into a whiskey mash, again in a test quantity. They scaled up from there.
Because it took so much time and effort to capture and propagate a good strain, the yeast-maker would then go to great lengths to preserve it and keep it from mutating to the point where it became unusable. They would keep it in a sealed container called a dona jug. They might divide it up into several jugs for safe-keeping.
Making a batch of yeast for production meant taking a small amount from the jug and adding it to fresh yeast mash. This yeast mash recipe might be the same as the one used for capturing the yeast, or a variation on that, but it still wasn't the same as the whiskey mash. To set the fermenters to make a batch of whiskey takes a lot of yeast prepared in this way. It's a tedious, several-day process usually done by an apprentice.
When refrigeration came along that helped a lot, since it slowed propagation down, which helped the yeast last longer. Before refrigeration they used root cellars and wells to keep the dona jugs cool. Keeping a particular yeast productive also took luck and skill but they would all mutate eventually and have to be discarded. Today's jug yeasts don't because they have been scientifically purified.
They did all this not because they fancied themselves as artisans. They did it because they didn't have a choice. Their alternative wasn't commercial yeast, it was spontaneous fermentation, which is what they were trying to avoid.
So one can accept why no one does this today. Even people who still use jug yeast use jug yeast that is scientifically supported. I would think that the impulse to make it from scratch is the same as the impulse to make bread from scratch even in an era when you can go to the store and buy good bread. It is a chance to make something that is truly, if only minutely, unique.
Two parallels that reach different conclusions might be malting and milling. Kentucky and Tennessee do not have any tradition of people doing their own malting. They didn't malt because they didn't have to. Acceptable malt was always readily available. Yet they always did their own milling and still do. Why? Either because millers couldn't supply the grind they wanted or because millers couldn't supply distilleries cost-effectively.
I confess yeast-making has a romantic appeal for me but if you want to recapture some of what has been lost in the industrialization of distilling, how better?